The Billion-Year Gas Inside a Birthday Balloon

Most of us have gone to a party store to buy balloons. You pick out a color, an employee fills it from a cylinder behind the register, and it rises as if possessed by a spirit. But the stuff inside that balloon—helium—has been waiting billions of years to get there. As Washington University chemistry professor Sophia Hayes explains, "Where that helium comes from is the decay of radioactive elements. And as they decay, they spit out an atom of helium. So every time you see a balloon, that's billions of years of the age of the Earth."

It may seem silly that a billion-year process ends up inside a "Happy Birthday" balloon. But helium's real value lies elsewhere: it cools MRI machines, manufactures semiconductors, and tests leaks in rocket ships. Getting it out of the ground is a multi-billion dollar business—and a surprisingly fragile one.

What Makes Helium Special

Helium is one of only six naturally occurring noble gases—highly stable elements that rarely form compounds with other substances. "They're called noble by analogy to aristocrats, who don't mix with the common folk," Hayes says. This stability means helium can be used without worrying about undesirable reactions.